Influence of mycorrhizal fungi on soil geochemistry and plant uptake of cadmium and zinc: greenhouse and soil studies of Palmerton Zinc Superfund Site, Pennsylvania, u.s.a.

摘要

The application of bioremediation as a means to ameliorate potentially toxic metals from contaminated soils has been on the forefront of sustainable technologies in the field of environmental studies. Conventional methods available for soil remediation are employed in both in situ or ex situ and these are: soil flushing, solidification/stabilization, vitrification, electrokinetics, chemical reduction/oxidation, soil washing, and excavation. In general, these technologies are limited by their applicability to small areas and the high costs to execute. The use of biota, in particular fungi and trees, has been an emerging low-cost and "environmentally-friendly" alternative to conventional technologies. In this study, I evaluate four soils collected from the Lehigh Gap Wildlife Refuge and Nature Center adjacent to the Palmerton Zinc Superfund Site by using commonly used single extraction methods and the revised European Bureau of Common References (BCR) sequential extraction to determine availability of Cd and Zn. I also explore how the rhizosphere-based method (RBM) that mimics rhizosphere conditions compares to the liquid cultures of the ectomycorrhizal fungus Paxillus involutus to interpret change in metal availability and the potential for environmental risk associated with fungal inoculation of soils when used to aid remediation projects. Additionally, comparison between extractants (EDTA, DTPA, Mehlich-III, Fraction 1 and Pseudototal of the revised BCR sequential extraction method) that evaluate plant availability to determine the efficacy of the previous mentioned extractants. Findings were that both components of the BCR method grossly overestimates both Cd and Zn compared to aforementioned extractants. Additionally, fungal liquid performed similarly to the Mehlich-III as comparable extractant for determining Cd and Zn availability, where fungal liquid and RBM had similar extractability for Zn only.;Work was also done to investigate effects of P. involutus and a Populus hybrid on fractionation of metals in these soils by the revised BCR sequential extraction method. Findings suggest that availability and mobility of Cd and Zn in contaminated soils can be altered significantly by P. involutus and Populus and plant uptake of Cd is greater than Zn. With further research with more varieties of hybrid poplars and mycorrhizal fungi more effective symbionts can be chosen to aid in remediating metal contaminated sites that may pose a risk to the environment and human health.